Stabilized vesicant agent



Patented Jan. 2, 1951 2,536,482 STABILIZED VESICANT AGENT William H.Wood, Arden, DeL, assignor, by mesne assignments, to the United Statesof America as represented by the Secretary of War No Drawing.Application December 11, 1945, Serial No. 634,408

3 Claims.

'portant, in this country, is the Levinstein proc- The product of thisprocess is known to ess. those skilled in the art as Levinstein mustard.

Levinstein mustard is a reatively impure product and the dichlorethylsulfide content thereof is in the neighborhood of 70%. The impurities inLevinstein mustard ar of a complex nature and have not yet beencompletely determined to this date but are essentially polysulfides ofthe composition (C1CH2CH2)2SX.

Levinstein mustard is a very effective Vesicant agent and is economicalfor use in chemical warfare, however, it does have the serious defect ofattacking steel containers during long periods of storage. Although theexact mechanism of the chemical reaction between Levinstein mustard andsteel containers is not known, it is known that mustard, stored in steelcontainers, becomes contaminated with iron. Levinstein mustard stored inglass containers, or in steel containers coated with a properly baked-onsuitable lacquer, does not deteriorate.

For certain technical purposes it is necessary to disseminate vesicantssuch as mustard from airplanes. Heretofore, the effectiveness of thevesicants when sprayed from airplanes has been considerably less thanthe maximum effectiveness obtainable, because a large portion of theVesicant material is broken up into a very fine mist and acorrespondingly smaller fraction reaches the objective in the form oflarge drops. The higher the altitude and the greater the airp ane speed,the

greater is the proportion of the fine mist and the less effective theVesicant spray.

Vesicant agents in liquid form are most effective against personnel andmaterial in t e form of fairly large drops and the loss of eifectivenessof airplane sprays due to the formation of fine mist is veryconsiderable. vesicants in the form of fine mists have a decreasingpenetrating action through protective clothing and a smaller amount ofprotection is required against them. Heretol fore, it was necessary foran airplane to drop to very low altitudes (75500 ft.) and to spray at alow air speed to obtain proper sized drops in a Vesicant spray.

Another very important obstacle in the spray- .ing of vesicants fromairplanes has, been the inability to aim the spray to fall upon thetarget with any degree of accuracy. Vesicant sprays in the form ofrelatively large drops can be accurately aimed but fine sprays and mistsfail to hit the target area with any degree of precision.

The same general principles also apply to the dissemination of vesicantsby artillery shell. The use of high explosive charges to burst the shellresults in the creation of a fine mist and consequent dispersion of theVesicant.

It has therefore been found to be necessary to thicken the Vesicantagents in order to obtain proper drop size and to eliminate the loss ofagent, the loss of accuracy, and the necessity for projecting the sprayfrom low altitudes at low plane speeds. The addition of certainpolymeric materials to Vesicant agents in order to thicken the agent toobtain the required properties has been proposed. However, I havediscovered that Vesicant agents thus thickened have the defect ofdecreasing in viscosity when the agent is contaminated with iron.

I have discovered that in iron-contaminated mustard containing apolymeric thickener there is formed a complex of low solubility betweenthe polymeric thickener and the iron, which precipitates and lowers theviscosity of the supernatant mustard below that required for itsdissemination in proper drop size.

Since mustard is normally stored in steel containers both before andafter thickening, contamination with iron, always occurs and lowering ofviscosity due to the above described reaction is encountered.

I have discovered that this serious defect can be remedied by theaddition of certain stabilizers to the mustard either before or afterthickening, in order to prevent the precipitation of the ironthiekenercomplex and to thus maintain the desired viscosity of the Vesicantagent.

I have found that heterocyclic aromatic nitrogen bases of any degree ofpurity are suitable as stabilizers for thickened mustard.

Any of the crude aromatic nitrogen bases or fractions of crude basesobtained from coal tar or petroleum, or pure bases such as pyridine,quinoline, and picoline may be used. Ordinarily, an amount of nitrogenbase equal to 2% of the weight of the mustard is sufiicient. This amountwill neutralize all t e iron in mustard containing up to 1% iron,calculated as ferrous chloride. If more than 1% iron is present,proportionally larger amounts, e. g., up to 5% of nitrogen bases, may beused. When mixing in the plant, it is preferable to add the nitrogenbase to the mustard first, to prevent precipitation of theiron-thickener complex when the thickener is added. When mixing in thefield, the nitrogen base may be added either to the thickener solutionor to the mustard, the thickener and mustard then being combined.Whatever the mixing method employed, the nitrogen base may be addedeither to the thickener solution or to the mustard, the thickener andmustard then being combined. Whatever the mixing method employed, thenitrogen base may be used in conjunction with non-aromatic amines, suchas hexamethylenetetramine, which are effective anti-corrosion agents formustard. These nitrogen bases havebeen tested in mustard, thickened withmethyl methacrylate polymer and methly methacrylatemethyl acrylateinterpolymer, and they arealso eifective in mustard containing any otherpoly.- meric thickener, e. g., polystyrene.

This invention contemplates compositions comprising iron-contaminatedmustard containing a polymeric thickener soluble therein, and a smallamount of a heterocyclic aromatic nitrogen base, i. e., a nitrogen basein which the nitrogen is part of an aromatic ring, 1. e., a ringcontaining conjugated double bonds. Nitrogen bases of this type havebeen found to be particularly eifective in preventing the iron normallypresent in ordinary mustard (particularly that stored in steelcontainers) from altering, undesirably; the viscosity characteristics ofthe thickened composition. This is of significance since, if the iron isnot removed or deactivated; it will form a complex of low solubilitywith the polymeric thickener and precipitate as :a sludge, particularlyat low temperatures. The precipitation of the iron-thickener complex re-7 moves the thickener and thus lowers the viscosity ExampleI.-FieZd-mia:ing process A steam-jacketed iron vessel fitted with areflux condenser and mechanical stirrer is charged with 652 parts ofbenzene and 87 parts of quincline residue (from distillat on ofquinoline from coal tap-contains high boiling nitrogen bases ofouinoline type), and 33 parts of pulverized methi yl methacrylatepolymer sheeting are added with stirring. The temperature of the mixtureis raised to 50-55 C. and agitation continued at this temperature untila product of constant viscosity is obtained, about 4 to 5 hours beingrequired. This solution, which will have a viscosity in the range of 8to 25 stokes at 25 C., is suit.- able for mixing with mustard in thefield. In thecase of Levinstein mustard containing, e. g., LS-0.6% iron(calculated as ferrous chloride), 'l5iparts of the solution is added to85"parts-of mustard and the mixture agitated gently for 1'5-20 minutesatroom temperature. The resulting smooth solution has a viscosityof'about Example II.-Plant mixing process A vessel equipped with amechanical stirrer and means for heating is charged with 1586 parts ofmustard of the quality used'in Example 1, "32 parts of a mixture ofpyridine bases, and 32 parts of pulverized methyl methacrylate' polymersheeting are added. The mixture is stirred atf40 to 50C. for 3 hours,then cooled to room. 2, 9

. 4 temperature and stirred overnight. The resulting smooth solution hasa viscosity of 4.44 stokes at 10 C., with no sludge formation, whereas acontrol composition containing no pyridine base forms a sludgeimmediately when cooled to 10 C.

Attempts have been made to stabilize thickened Levinstein mustard by theaddition of a non-aromatic heterocyclic amine but the results were notsatisfactory. The only amines Which I have found to be eifective forthis purpose are the heterocyclic aromatic nitrogen basis which containsa conjugate double bond system.

Accordingly, an object of my invention is to stabilize thickened mustardgas in order to maintainproper viscosity. Another object of thisinvention is to provide a practical and effective means of stabilizingLevinstein mustard so that it can be thickened and so that the viscosityof the thickened agent can be controlled in'order that proper drop sizemay be obtained upon dissemination of the agent.

My invention, by the addition of a small amount of a heterocyclicaromatic amine, prevents the precipitation of iron-thickener complex andthus maintains the desired viscosity of agent.

The nature of this invention having been broadly outlined above and thepreferred sinbodiments specifically pointed out, it will beapparent tothose skilled in the art that certain modifications and additionalformulations can be employed. Accordingly, it is intended that theforegoing descriptive material be interpreted as illustrative and not ina limiting sense.

Iclaim:

1. A composition of matter comprising Levinstein mustard containing fromabout 0.5% to 0.6% of iron calculated as ferrous chloride, thickenedwith a polymeric material selected fromthe group consisting of methylmethacrylate polyusers and of methyl-methacrylate-acrylate interpolymersand stabilized with from'about 2% to about 5% of a compoundselected fromthe group consisting of pyridine, quinoline and piccline, saidcomposition having a viscosity of about a 3. .A'composition of mattercomprising'about 1586 parts by weight of Levinstein mustardconta-iningabout i).5-0.6% of iron calculated as ferrous chloride, about 32 partsby weight of pyridine bases, and about 32 parts by weight of methylmethacrylate polymer, said composition of matter having a viscosity ofabout 4.44 stokes at 10 C. with no sludge formation.

WILLIAM H. woon.

aernnsncns crrnn The following references are of record in the file o ths pate t:

UNITED STATES P ATENTS Number Name Date 2,260,420 Young Oct. 28, 1941Hum Feb. 28, 1950

1. A COMPOSITION OF MATTER COMPRISING LEVINSTEIN MUSTARD CONTAINING FROMABOUT 0.5% TO 0.6% OF IRON CALCULATED AS FERROUS CHLORIDE, THICKENEDWITH A POLYMERIC MATERIAL ELECTED FROM THE GROUP CONSISTING OF METHYLMETHACRYLATE POLYMERS AND METHYL-METHACRYLATE-ACRYLATE INTERPOLYMERS ANDSTABILIZED WITH FROM ABOUT 2% TO ABOUT 5% OF A COMPOUND SELECTED FROMTHE GROUP CONSISTING OF PYRIDINE, QUINOLINE AND PICOLINE, SAIDCOMPOSITION HAVING A VISCOSITY OF ABOUT 0.42 STROKE AT 10* C. WITH NOSLUDGE FORMATION.